The walls on Columbia Parkway were built in the 1930s, complete with "weep holes" to allow runoff to drain away from the road. They were re-enforced in the 1990s, but could still be vulnerable.

Eyes will also be on Elberon Avenue, where the retaining wall has given way before, leaving trees, soil, and rocks blocking lanes.

Many of the problems are caused by both nature and human error.

“The hillsides along Columbia Parkway, they're steep, they're composed of unstable soil, back in the 1930s, when they constructed the wall, they over-steepened the lower portion of the slopes,” Cincinnati Engineering Geologist Richard Pohana said.

The whole Tri-State will be on guard for the possibility of landslides. As much as five inches of rain is expected between Friday night and Sunday morning.